(p. 25) ~Cellulose sulphocarbonate.~--Further investigations of the
reaction of formation as well as the various reactions of decomposition
of the compound, have not contributed any essential modification or
development of the subject as originally described in the author's first
communications. A large amount of experimental matter has been
accumulated in view of the ultimate contribution of the results to the
general theory of colloidal solutions. But viscose is a complex product
and essentially variable, through its pronounced tendency to progressive
decomposition with reversion of the cellulose to its insoluble and
uncombined condition. The solution for this reason does not lend itself
to exact measurement of its physical constants such as might elucidate
in some measure the progressive molecular aggregation of the cellulose
in assuming spontaneously the solid (hydrate) form. Reserving the
discussion of these points, therefore, we confine ourselves to recording
results which further elucidate special points.
_Normal and other celluloses._--We may certainly use the sulphocarbonate
reaction as a means of defining a normal cellulose. As already pointed
out, cotton cellulose passes quantitatively through the cycle of
treatments involved in solution as sulphocarbonate and decomposition of
the solution with regeneration as structureless or amorphous cellulose
(hydrate).
Analysis of this cellulose shows a fall of carbon percentage from 44.4
to 43.3, corresponding with a change in composition from
C_{6}H_{10}O_{5} to 4C_{6}H_{10}O_{5}.H_{2}O. The partial hydrolysis
affects the whole molecule, and is limited to this effect, whereas, in
the case of celluloses of other types, there is a fractionation of the
mass, a portion undergoing a further hydrolysis to compounds of lower
molecular weight and permanently soluble. Thus in the case of the wood
celluloses the percentage recovered from solution as viscose is from 93
to 95 p.ct. It is evident that these celluloses are not homogeneous. A
similar conclusion results from the presence of furfural-yielding
compounds with the observation that the hydrolysis to soluble
derivatives mainly affects these derivatives. In the empirical
characterisation of a normal cellulose, therefore, we may include the
property of quantitative regeneration or recovery from its solution as
sulphocarbonate.
In the use of the word 'normal' as applied to a 'bleached' cotton, we
have further to show in what respects the sulphocarbonate reaction
differentiates the bleached or purified cotton cellulose from the raw
product. The following experiments may be cited: Specimens of American
and Egyptian cottons in the raw state, freed from mechanical, i.e.
non-fibrous, impurities, were treated with a mercerising alkali, and the
alkali-cotton subsequently exposed to carbon disulphide. The product of
reaction was further treated as in the preparation of the ordinary
solution; but in place of the usual solution, structureless and
homogeneous, it was observed to retain a fibrous character, and the
fibres, though enormously swollen, were not broken down by continued
vigorous stirring. After large dilution the solutions were filtered, and
the fibres then formed a gelatinous mass on the filters. After
purification, the residue was dried and weighed. The American cotton
yielded 90.0 p.ct., and the Egyptian 92.0 p.ct. of its substance in the
form of this peculiar modification. The experiment was repeated,
allowing an interval of 24 hours to elapse between the conversion into
alkali-cotton and exposure of this to the carbon disulphide. The
quantitative results were identical.
There are many observations incidental to chemical treatments of cotton
fabrics which tend to show that the bleaching process produces other
effects than the mere removal of mechanical impurities. In the
sulphocarbonate reaction the raw cotton, in fact, behaves exactly as a
compound cellulose. Whether the constitutional difference between raw
and bleached cotton, thus emphasised, is due to the group of components
of the raw cotton, which are removed in the bleaching process, or to
internal constitutional changes determined by the bleaching treatments,
is a question which future investigation must decide.
_The normal sulphocarbonate (viscose)._--In the industrial applications
of viscose it is important to maintain a certain standard of composition
as of the essential physical properties of the solution, notably
viscosity. It may be noted first that, with the above-mentioned
exception, the various fibrous celluloses show but slight differences in
regard to all the essential features of the reactions involved. In the
mercerising reaction, or alkali-cellulose stage, it is true the
differences are considerable. With celluloses of the wood and straw
classes there is a considerable conversion into soluble
alkali-celluloses. If treated with water these are dissolved, and on
weighing back the cellulose, after thorough washing, treatment with
acid, and finally washing and drying, it will be found to have lost from
15 to 20 p.ct. in weight. The lower grade of celluloses thus dissolved
are only in part precipitated in acidifying the alkaline solution. On
the other hand, after conversion into viscose, the cellulose when
regenerated re-aggregates a large proportion of these lower grade
celluloses, and the final loss is as stated above, from 5 to 7 p.ct.
only.
Secondly, it is found that all the conditions obtaining in the
alkali-cellulose stage affect the subsequent viscose reaction and the
properties of the final solution. The most important are obviously the
proportion of alkali to cellulose and the length of time they are in
contact before being treated with carbon disulphide. An excess of
alkali beyond the 'normal' proportion--viz. 2NaOH per 1 mol.
C_{6}H_{10}O_{5}--has little influence upon the viscose reaction, but
lowers the viscosity of the solution of the sulphocarbonate prepared
from it. But this effect equally follows from addition of alkali to the
viscose itself. The alkali-cellulose changes with age; there is a
gradual alteration of the molecular structure of the cellulose, of which
the properties of the viscose when prepared are the best indication.
There is a progressive loss of viscosity of the solution, and a
corresponding deterioration in the structural properties of the
cellulose when regenerated from it--especially marked in the film form.
In regard to viscosity the following observations are typical:--
(a) A viscose of 1.8 p.ct. cellulose prepared from an
alkali-cellulose (cotton) fourteen days old.
(b) Viscose of 1.8 p.ct. cellulose from an alkali-cellulose
(cotton) three days old.
(c) Glycerin diluted with 1/3 vol. water.
a b b c
Diluted with
equal vol.
water
Times of flow of equal volumes from 112 321 103 170
narrow orifice in seconds
Similarly the cellulose in reverting to the solid form from these
'degraded' solutions presents a proportionate loss of cohesion and
aggregating power expressed by the inferior strength and elasticity of
the products. Hence, in the practical applications of the product where
the latter properties are of first importance, it is necessary to adopt
normal standards, such as above indicated, and to carefully regulate all
the conditions of treatment in each of the two main stages of reaction,
so that a product of any desired character may be invariably obtained.
Incidentally to these investigations a number of observations have been
made on the alkali-cellulose (cotton) after prolonged storage in closed
vessels. It is well known that starch undergoes hydrolysis in contact
with aqueous alkalis of a similar character to that determined by acids
[Bechamp, Annalen, 100, 365]. The recent researches of Lobry de Bruyn
[Rec. Trav. Chim. 14, 156] upon the action of alkaline hydrates in
aqueous solution on the hexoses have established the important fact of
the resulting mobility of the CO group, and the interchangeable
relationships of typical aldoses and ketoses. It was, therefore, not
improbable that profound hydrolytic changes should occur in the
cellulose molecule when kept for prolonged periods as alkali-cellulose.
We may cite an extreme case. A series of products were examined after
12-18 months' storage. They were found to contain only 3-5 p.ct.
'soluble carbohydrates'; these were precipitated by Fehling's solution
but without reduction on boiling. They were, therefore, of the cellulose
type. On acidifying with sulphuric acid and distilling, traces only of
volatile acid were produced. It is clear, therefore, that the change of
molecular weight of the cellulose, the disaggregation of the undoubtedly
large molecule of the original 'normal' cellulose--which effects are
immediately recognised in the viscose reactions of such products--are of
such otherwise limited character that they do not affect the
constitution of the unit groups. We should also conclude that the
cellulose type of constitution covers a very wide range of minor
variations of molecular weight or aggregation.
The resistance of the normal cellulose to the action of alkalis under
these hydrolysing conditions should be mentioned in conjunction with the
observations of Lange, and the results of the later investigations of
Tollens, on its resistance to 'fusion' with alkaline hydrates at high
temperatures (180 deg.). The degree of resistance has been established only
on the empirical basis of weighing the product recovered from such
treatment. The product must be investigated by conversion into typical
cellulose derivatives before we can pronounce upon the constitutional
changes which certainly occur in the process. But for the purpose of
this discussion it is sufficient to emphasise the extraordinary
resistance of the normal cellulose to the action of alkalis, and to
another of the more significant points of differentiation from starch.
_Chemical constants of cellulose sulphocarbonate (solution)._--In
investigations of the solutions we make use of various analytical
methods, which may be briefly described, noting any results bearing upon
special points.
_Total alkali._--This constant is determined by titration in the usual
way. The cellulose ratio, C_{6}H_{10}O_{5} : 2NaOH, is within the
ordinary error of observation, 2 : 1 by weight. A determination of alkali
therefore determines the percentage of cellulose.
_Cellulose_ may be regenerated in various ways--viz. by the action of
heat, of acids, of various oxidising compounds. It is purified for
weighing by boiling in neutral sulphite of soda (2 p.ct. solution) to
remove sulphur, and in very dilute acids (0.33 p.ct. HCl) to decompose
residues of 'organic' sulphur compounds. It may also be treated with
dilute oxidants. After weighing it may be ignited to determine residual
inorganic compounds.
_Sulphur._--It has been proved by Lindemann and Motten [Bull. Acad. R.
Belg. (3), 23, 827] that the sulphur of sulphocarbonates (as well as of
sulphocyanides) is fully oxidised (to SO_{3}) by the hypochlorites
(solutions at ordinary temperatures). The method may be adapted as
required for any form of the products or by-products of the viscose
reaction to be analysed for _total sulphur_.
The sulphur present in the form of dithiocarbonates, including the
typical cellulose xanthogenic acid, is approximately isolated and
determined as CS_{2} by adding a zinc salt in excess, and distilling off
the carbon disulphide from a water bath. From freshly prepared solutions
a large proportion of the disulphide originally interacting with the
alkali and cellulose is recovered, the result establishing the general
conformity of the reaction to that typical of the alcohols. On keeping
the solutions there is a progressive interaction of the bisulphide and
alkali, with formation of trithiocarbonates and various sulphides. In
decomposing these products by acid reagents hydrogen sulphide and free
sulphur are formed, the estimation of which presents no special
difficulties.
In the spontaneous decomposition of the solution a large proportion of
the sulphur resumes the form of the volatile disulphide. This is
approximately measured by the loss in total sulphur in the following
series of determinations, in which a viscose of 8.5 p.ct. strength
(cellulose) was dried down as a thin film upon glass plates, and
afterwards analysed:
(a) Proportion of sulphur to cellulose (100 pts.) in original.
(b) After spontaneous drying at ordinary temperature.
(c) After drying at 40 deg.C.
(d) As in (c), followed, by 2 hours' heating at 98 deg..
(e) As in (c), followed by 5 hours' heating at 98 deg..
a b c d e
Total sulphur 40.0 25.0 31.0 23.7 10.4
The dried product in (b) and (c) was entirely resoluble in water; in
(d) and (e), on the other hand, the cellulose was fully regenerated,
and obtained as a transparent film.
_Iodine reaction._--Fresh solutions of the sulphocarbonate show a fairly
constant reaction with normal iodine solution. At the first point, where
the excess of iodine visibly persists, there is complete precipitation
of the cellulose as the bixanthic sulphide; and this occurs when the
proportion of iodine added reaches 3I_{2} : 4Na_{2}O, calculated to the
total alkali.
_Other decompositions._--The most interesting is the interaction which
occurs between the cellulose xanthogenate and salts of ammonia, which is
taken advantage of by C. H. Stearn in his patent process of spinning
artificial threads from viscose. The insoluble product which is formed
in excess of the solution of ammonia salt is free from soda, and
contains 9-10 p.ct. total sulphur. The product retains its solubility in
water for a short period. The solution may be regarded as containing the
ammonium cellulose xanthate. This rapidly decomposes with liberation of
ammonia and carbon disulphide, and separation of cellulose (hydrate). As
precipitated by ammonium-chloride solution the gelatinous thread
contains 15 p.ct. of cellulose, with a sp.gr. 1.1. The process of
'fixing'--i.e. decomposing the xanthic residue--consists in a short
exposure to the boiling saline solution. The further dehydration, with
increase of gravity and cellulose content, is not considerable. The
thread in its final air-dry state has a sp.gr. 1.48.
* * * * *
~Cellulose Benzoates.~--These derivatives have been further studied by the
authors. The conditions for the formation of the monobenzoate
[C_{6}H_{9}O_{4}.O.CO.Ph] are very similar to those required for the
sulphocarbonate reaction. The fibrous cellulose (cotton), treated with a
10 p.ct. solution NaOH, and subsequently with benzoyl chloride, gives
about 50 p.ct. of the theoretical yield of monobenzoate. Converted by 20
p.ct. solution NaOH into alkali-cellulose, and with molecular
proportions as below, the following yields were obtained:--
Calc. for
Monobenzoate
(a) C_{6}H_{10}O_{5} : 2.0-2.5 NaOH : C_{6}H_{5}.COCl-- 150.8}
}164.0
(b) C_{6}H_{10}O_{5} : 2.0-2.5 NaOH : 1.5 mol. C_{6}H_{5}COCl 159.0}
An examination of (a) showed that some dibenzoate (about 7 p.ct.) had
been formed. The product () was exhaustively treated with cuprammonium
solution, to which it yielded about 20 p.ct. of its weight, which was
therefore unattacked cellulose.
Under conditions as above, but with 2.5 mol. C_{6}H_{5}COCl, a careful
comparison was made of the behaviour of the three varieties of cotton,
which were taken in the unspun condition and previously fully bleached
and purified.
___________________________________________________________________
| | | | |
| | Sea Island | Egyptian | American |
|________________________________|____________|__________|__________|
| | | | |
| Aggregate yield of benzoate | 153 | 148 | 152 |
| Moisture in air dry state | 5.28 | 5.35 | 5.15 |
| Proportion of dibenzoate p.ct. | 8.30 | 13.70 | 9.4 |
| Yield of cellulose by | 58.0 | 54.0 | 58.3 |
| saponification | | | |
|________________________________|____________|__________|__________|
It appears from these results that the benzoate reaction may proceed to
a higher limit (dibenzoate) in the case of Egyptian cotton. This would
necessarily imply a higher limit of 'mercerisation,' under equal
conditions of treatment with the alkaline hydrate. It must be noted that
in the conversion of the fibrous cellulose into these (still) fibrous
monobenzoates, there are certain mechanical conditions imported by the
structural features of the ultimate fibres. For the elimination of the
influence of this factor a large number of quantitative comparisons will
be necessary. The above results are therefore only cited as typical of a
method of comparative investigation, more especially of the still open
questions of the cause of the superior effects in mercerisation of
certain cottons (see p. 23). It is quite probable that chemical as well
as structural factors co-operate in further differentiating the cottons.
Further investigation of the influence upon the benzoate reaction, of
increase of concentration of the soda lye, used in the preliminary
alkali cellulose reaction, from 20 to 33 p.ct. NaOH, established (1)
that there is no corresponding increase in the benzoylation, and (2)
that this ester reaction and the sulphocarbonate reaction are closely
parallel, in that the degree and limit of reaction are predetermined by
the conditions of formation of the alkali cellulose.
_Monobenzoate_ prepared as above described is resistant to all solvents
of cellulose and of the cellulose esters, and is therefore freed from
cellulose by treatment with the former, and from the higher benzoate by
treatment with the latter. Several of these, notably pyridine, phenol
and nitrobenzene, cause considerable swelling and gelatinisation of the
fibres, but without solution.
_Structureless celluloses_ of the 'normal' type, and insoluble therefore
in alkaline lye, treated under similar conditions to those described
above for the fibrous celluloses, yield a higher proportion of
dibenzoate. The following determinations were made with the cellulose
(hydrate) regenerated from the sulphocarbonate:--
Mol. proportions of reagents Yield Dibenzoate p.ct.
C_{6}H_{10}O_{5} : 2NaOH : 2BzCl 145 34.7
[Caustic soda at 10 per cent. NaOH]
C_{6}H_{10}O_{5} : 4NaOH : 2BzCl 162 62.7
[Caustic soda at 20 per cent. NaOH]
_Limit of reaction._--The cellulose in this form having shown itself
more reactive, it was taken as the basis for determining the maximum
proportion of OH groups yielding to this later reaction. The systematic
investigations of Skraup [Monatsh. 10, 389] have determined that as
regards the interacting groups the molecular proportions 1 OH : 7 NaOH :
5 BzCl, ensure complete or maximum esterification. The maximum of OH
groups in cellulose being 4, the reagents were taken in the proportion
C_{6}H_{10}O_{5} : 4 [7 NaOH : 5 BzCl]. The yield of crude product, after
purifying as far as possible from the excess of benzoic acid, was 240
p.ct. [calculated for dibenzoate 227 p.ct.]. On further investigating
the crude product by treatment with solvents, it was found to have still
retained benzoic acid. There was also present a proportion of only
partially attacked cellulose (monobenzoate). The soluble benzoate
amounted to 90 p.ct. of the product. It may be generally concluded that
the dibenzoate represents the normal maximum but that with the hydrated
and partly hydrolysed cellulose molecule, as obtained by regeneration
from the sulphocarbonate, other OH groups may react, but they are only a
fractional proportion in relation to the unit group C_{6}H_{10}O_{5}. In
this respect again there is a close parallelism between the
sulphocarbonate and benzoyl-ester reactions.
_The dibenzoate_, even when prepared from the fibrous celluloses, is
devoid of structure, and its presence in admixture with the fibrous
monobenzoate is at once recognised as it constitutes a structureless
incrustation. Under the microscope its presence in however minute
proportion is readily observed. As stated it is soluble in certain of
the ordinary solvents of the cellulose esters, e.g. chloroform, acetic
acid, nitrobenzene, pyridine, and phenol. It is not soluble in ether or
alcohol.
_Hygroscopic moisture of benzoates._--The crude monobenzoate retains
5.0-5.5 p.ct. moisture in the air-dry condition. After removal of the
residual cellulose this is reduced to 3.3 p.ct. under ordinary
atmospheric conditions. The purified dibenzoates retain 1.6 p.ct. under
similar conditions.
_Analysis of benzoates._--On saponification of these esters with
alcoholic sodium hydrate, anomalous results are obtained. The acid
numbers, determined by titration in the usual way, are 10-20 p.ct. in
excess of the theoretical, the difference increasing with the time of
boiling. Similarly the residual cellulose shows a deficiency of 5-9
p.ct.
It is by no means improbable that in the original ester reaction there
is a constitutional change in the cellulose molecule causing it to break
down in part under the hydrolysing treatment with formation of acid
products. This point is under investigation. Normal results as regards
acid numbers, on the other hand, are obtained by saponification with
sodium ethylate in the cold, the product being digested with the
half-saturated solution for 12 hours in a closed flask.
The following results with specimens of mono- and dibenzoate, purified,
as far as possible, may be cited:
Combustion results Saponification results
Calc. C_{6}H_{5}.COOH Calc. Cellulose Calc.
Monobenzoate C 56.60 58.65}
H 5.06 5.26} 46.0 45.9 58.0 60.8
Dibenzoate C 63.10 64.86}
H 3.40 4.86} 65.5 66.6 34.3 40.3
The divergence of the numbers, especially for the dibenzoate, in the
case of the hydrogen, and yield of cellulose on hydrolysis are
noteworthy. They confirm the probability of the occurrence of secondary
changes in the ester reactions.
_Action of nitrating acid upon the benzoates._--From the benzoates above
described, mixed nitro-nitric esters are obtained by the action of the
mixture of nitric and sulphuric acids. The residual OH groups of the
cellulose are esterified and substitution by an NO_{2} group takes place
in the aromatic residue, giving a mixed nitric nitrobenzoic ester. The
analysis of the products points to the entrance of 1 NO_{2} group in the
benzoyl residue in either case; in the cellulose residue 1 OH readily
reacts. Higher degrees of nitration are attained by the process of
solution in concentrated nitric acid and precipitation by pouring into
sulphuric acid. In describing these mixed esters we shall find it
necessary to adopt the C_{12} unit formula.
In analysing these products we have employed the Dumas method for _total
nitrogen_. For the O.NO_{2} groups we have found the nitrometer and the
Schloesing methods to give concordant results. For the NO_{2} groups it
was thought that Limpricht's method, based upon reduction with stannous
chloride in acid solution (HCl), would be available. The quantitative
results, however, were only approximate, owing to the difficulty of
confining the reduction to the NO_{2} groups of the nitrobenzoyl
residue. By reduction with ammonium sulphide the O.NO_{2} groups were
entirely removed as in the case of the cellulose nitrates; the NO_{2}
was reduced to NH_{2} and there resulted a cellulose amidobenzoate,
which was diazotised and combined with amines and phenols to form yellow
and red colouring matters, the reacting residue remaining more or less
firmly combined with the cellulose.
_Cellulose dinitrate-dinitrobenzoate, and cellulose
trinitrate-dinitrobenzoate._--On treating the fibrous benzoate--which is
a dibenzoate on the C_{12} basis--with the acid mixture under the usual
conditions, a yellowish product is obtained, with a yield of 140-142
p.ct. The nitrobenzoate is insoluble in ether alcohol, but is soluble in
acetone, acetic acid, and nitrobenzene. In purifying the product the
former solvent is used to remove any cellulose nitrates. To obtain the
maximum combination with nitroxy-groups, the product was dissolved in
concentrated nitric acid, and the solution poured into sulphuric acid.
The following analytical results were obtained (a) for the product
obtained directly from the fibrous benzoate and purified as indicated,
(b) for the product from the further treatment of (a) as described:
Found Calc. for
(a) (b) Dinitrate Trinitrate
dinitrobenzoate dinitrobenzoate
Total Nitrogen 7.84 8.97 7.99 9.24
O.NO_{2} " 5.00 5.45 4.00 5.54
NO_{2} (Aromatic) 2.84 3.52 3.99 3.70
With the two benzoyl groups converted into nitro-benzoyl in each
product, the limit of the ester reaction with the cellulose residue is
reached at the third OH group.
The nitrogen in the amidobenzoate resulting from the reduction with
ammonium sulphide was 4.5 p.ct.--as against 5.0 p.ct. calculated. The
moisture retained by the fibrous nitrate--nitrobenzoate--in the air-dry
state was found to be 1.97 p.ct.
The product from the structureless dibenzoate or tetrabenzoate on the
C_{12} formula, was prepared and analysed with the following results:
Calc. for
Mononitrate tetranitrobenzoate
Total Nitrogen 6.76 7.25
O.NO_{2} " 1.30 1.45
NO_{2} " (Aromatic) 5.46 5.80
The results were confirmed by the yield of product, viz. 131 p.ct. as
against the calculated 136 p.ct. They afford further evidence of the
generally low limit of esterification of the cellulose molecule. From
the formation of a 'normal' tetracetate--i.e. octacetate of the C_{12}
unit--we conclude that 4/5 of the oxygen atoms are hydroxyl oxygen. Of
the 8 OH groups five only react in the mixed esters described above, and
six only in the case of the simple nitric esters. The ester reactions
are probably not simple, but accompanied by secondary reactions within
the cellulose molecule.
* * * * *
(p. 34) ~Cellulose Acetates.~--In the first edition (p. 35) we have
committed ourselves to the statement that 'on boiling cotton with acetic
anhydride and sodium acetate no reaction occurs.' This is erroneous. The
error arises, however, from the somewhat vague statements of
Schutzenberger's researches which are current in the text-books [e.g.
Beilstein, 1 ed. p. 586] together with the statement that reaction only
occurs at elevated temperatures (180 deg.). As a matter of fact, reaction
takes place at the boiling temperature of the anhydride. We have
obtained the following results with bleached cotton:
Yield Calc. for Monoacetate
C_{6}H_{7}O_{4}O.C_{2}H_{3}O
Ester reaction 121 p.ct. 125 p.ct.
{Cellulose 79.9 79.9
Saponification {
{Acetic acid 29.9 29.4
This product is formed without apparent structural alteration of the
fibre. It is entirely insoluble in all the ordinary solvents of the
higher acetates. Moreover, it entirely resists the actions of the
special solvents of cellulose--e.g. zinc chloride and cuprammonium. The
compound is in other respects equally stable and inert. The hygroscopic
moisture under ordinary atmospheric conditions is 3.2 p.ct.
_Tetracetate._--This product is now made on the manufacturing scale: it
has yet to establish its industrial value.
NITRIRUNG VON KOHLENHYDRATEN.
W. WILL und P. LENZE (Berl. Ber., 1898, 68).
~NITRATES OF CARBOHYDRATES.~
(p. 38) The authors have studied the nitric esters of a typical series
of the now well-defined carbohydrates--pentoses, hexoses, both aldoses
and ketoses--bioses and trioses, the nitrates being prepared under
conditions designed to produce the highest degree of esterification.
Starch, wood, gum, and cellulose were also included in the
investigations. The products were analysed and their physical properties
determined. They were more especially investigated in regard to
temperatures of decomposition, which were found to lie considerably
lower than that of the cellulose nitrates. They also show marked and
variable instability at 50 deg. C. A main purpose of the inquiry was to
throw light upon a probable cause of the instability of the cellulose
nitrates, viz. the presence of nitrates of hydrolysed products or
carbohydrates of lower molecular weight.
The most important results are these:
_Monoses._--The _aldoses_ are fully esterified, in the pentoses 4 OH, in
the hexoses 5 OH groups reacting. The pentose nitrates are comparatively
stable at 50 deg.; the hexose nitrates on the other hand are extremely
unstable, showing a loss of weight of 30-40 p.ct. when kept 24 hours at
this temperature.
Xylose is differentiated by tending to pass into an anhydride form
(C_{5}H_{10}O_{5}-H_{2}O) under this esterification. When treated in
fact with the mixed acids, instead of by the process usually adopted by
the authors of solution in nitric acid and subsequent addition of the
sulphuric acid, it is converted into the dinitrate
C_{5}H_{6}O_{2}.(NO_{3})_{2}.
_Ketoses_ (C_{6}).--These are sharply differentiated from the corresponding
aldoses by giving _tri_nitrates C_{6}H_{7}O_{2}(NO_{3})_{3} instead
of _penta_nitrates, the remaining OH groups probably undergoing internal
condensation. The products are, moreover, _extremely stable_. It is also
noteworthy that levulose gave this same product, the trinitrate of the
anhydride (levulosan) by both methods of nitration (_supra_).
_The bisaccharides or bioses_ all give the octonitrates. The degree of
instability is variable. Cane-sugar gives a very unstable nitrate. The
lactose nitrate is more stable. Thus at 50 deg. it loses only 0.7 p.ct. in
weight in eight days; at 75 deg. it loses 1 p.ct. in twenty-four hours, but
with a rapid increase to 23 p.ct. in fifty-four hours. The maltose
octonitrate melts (with decomposition) at a relatively high temperature,
163 deg.-164 deg.. At 50 deg.-75 deg. it behaves much like the lactose nitrate.
_Trisaccharide._--Raffinose yielded the product
C_{18}H_{21}O_{5}.(NO_{3})_{11}.
_Starch_ yields the hexanitrate (C_{12}) by both methods of nitration.
The product has a high melting and decomposing point, viz. 184 deg., and
when thoroughly purified is quite stable. It is noted that a yield of
157 p.ct. of this nitrate was obtained, and under identical conditions
cellulose yielded 170 p.ct.
_Wood gum_, from beech wood, gave a tetranitrate (C_{10} formula)
insoluble in all the usual solvents for this group of esters.
The authors point out in conclusion that the conditions of instability
and decomposition of the nitrates of the monose-triose series are
exactly those noted with the cellulose nitrates as directly prepared and
freed from residues of the nitrating acids. They also lay stress upon
the superior stability of the nitrates of the anhydrides, especially of
the ketoses.
NITRATED CARBOHYDRATES AS FOOD MATERIAL FOR MOULDS.
THOMAS BOKORNY (Chem. Zeit., 1896, 20, 985-986).
(p. 38) Cellulose trinitrate (nitrocellulose) will serve as a food
supply for moulds when suspended in distilled water containing the
requisite mineral matter and placed in the dark. The growth is rapid,
and a considerable quantity of the vegetable growth accumulates round
the masses of cellulose nitrate, but no growth is observed if mineral
matter is absent. Cellulose itself cannot act as a food supply, and it
seems probable that if glycerol is present cellulose nitrate is no
longer made use of.
NITRATION OF CELLULOSE, HYDROCELLULOSE, AND OXYCELLULOSE.
LEO VIGNON (Compt. rend., 1898, 126, 1658-1661).
(p. 38) Repeated treatment of cellulose, hydrocellulose, and
oxycellulose with a mixture of sulphuric and nitric acids in large
excess, together with successive analyses of the compounds produced,
showed that the final product of the reaction corresponded, in each
case, with the fixation of 11 NO groups by a molecule containing 24
atoms of carbon. On exposure to air, nitrohydrocellulose becomes yellow
and decomposes; nitro-oxycellulose is rather more stable, whilst
nitrocellulose is unaffected. The behaviour of these nitro-derivatives
with Schiff's reagent, Fehling's solution, and potash show that all
three possess aldehydic characters, which are most marked in the case of
nitro-oxycellulose. The latter also, when distilled with hydrochloric
acid, yields a larger proportion of furfuraldehyde than is obtained from
nitrocellulose and nitrohydrocellulose.
* * * * *
~CELLULOSE NITRATES-EXPLOSIVES.~
(p. 38) The uses of the cellulose nitrates as a basis for explosives are
limited by their fibrous character. The conversion of these products
into the structureless homogeneous solid or semi-solid form has the
effect of controlling their combustion. The use of nitroglycerin as an
agent for this purpose gives the curious result of the admixture of two
high or blasting explosives to produce a new explosive capable of
extended use for military purposes. The leading representatives of this
class of propulsive explosives, or 'smokeless powders' are ballistite
and cordite, the technology of which will be found fully discussed in
special manuals of the subject. Since the contribution of these
inventions to the development of cellulose chemistry does not go beyond
the broad, general facts above mentioned, we must refer the reader for
technical details to the manuals in question.
There are, however, other means of arriving at structureless cellulose
nitrates. One of these has been recently disclosed, and as the results
involve chemical and technical points of novelty, which are dealt with
in a scientific communication, we reproduce the paper in question,
viz.:--
A RE-INVESTIGATION OF THE CELLULOSE NITRATES.
A. LUCK and C. F. CROSS (J. Soc. Chem. Ind., 1900).
The starting-point of these investigations was a study of the nitrates
obtained from the structureless cellulose obtained from the
sulphocarbonate (viscose). This cellulose in the form of a fine meal was
treated under identical conditions with a sample of pure cotton
cellulose, viz. digested for 24 hours in an acid mixture containing in
100 parts HNO_{3}--24 : H_{2}SO_{4}--70 : H_{2}O--6: the proportion of
acid to cellulose being 60 : 1--. After careful purification the
products were analysed with the following results:
Soluble in
Nitrogen Ether alcohol
Fibrous nitrate 13.31 4.3 p.ct.
Structureless nitrate 13.35 5.6 "
Examined by the 'heat test' (at 80 deg.) and the 'stability test' (at 135 deg.)
they exhibited the usual instability, and in equal degrees. Nor were the
tests affected by exhaustive treatment with ether, benzene, and alcohol.
From this it appears that the process of solution as sulphocarbonate and
regeneration of the cellulose, though it eliminates certain constituents
of an ordinary bleached cellulose, which might be expected to cause
instability, has really no effect in this direction. It also appears
that instability may be due to by-products of the esterification process
derived from the cellulose itself.
The investigation was then extended to liquids having a direct solvent
action on these higher nitrates, more especially acetone. It was
necessary, however, to avoid this solvent action proper, and having
observed that dilution with water in increasing proportions produced a
graduated succession of physical changes in the fibrous ester, we
carried out a series of treatments with such diluted acetones.
Quantities of the sample (A), purified as described, but still unstable,
were treated each with five successive changes of the particular liquid,
afterwards carefully freed from the acetone and dried at 40 deg.C. The
products, which were found to be more or less disintegrated, were then
tested by the ordinary heat test, stability test, and explosion test,
with the results shown in the table on next page.
In this series of trials the sample 'A' was used in the condition of
pulp, viz. as reduced by the process of wet-beating in a Hollander. A
similar series was carried out with the guncotton in the condition in
which it was directly obtained from the ester reaction. The results were
similar to above, fully confirming the progressive character of the
stabilisation with increasing proportions of acetone. These results
prove that washing with the diluted acetone not only rendered the
nitrate perfectly stable, but that the product was more stable than that
obtained by the ordinary process of purification, viz. long-continued
boiling and washing in water. We shall revert to this point after
briefly dealing with the associated phenomenon of structural
disintegration. This begins to be well marked when the proportion of
acetone exceeds 80 p.ct. The optimum effect is obtained with mixtures of
90 to 93 acetone and 10 to 7 water (by volume). In a slightly diluted
acetone of such composition, the guncotton is instantly attacked, the
action being quite different from the gelatinisation which precedes
solution in the undiluted solvent. The fibrous character disappears, and
the product assumes the form of a free, bulky, still opaque mass, which
rapidly sinks to the bottom of the containing vessel. The disintegration
of the bulk of the nitrate is associated with
__________________________________________________________________________
| | | | | |
| | Proportions by volume | | | |
| |________________________| Temperature | Heat | Heat |
| | | | of | Test | Test |
| | Acetone | Water | Explosion | 80 deg. | 134 deg. |
|___________________|______________|_________|_____________|_______|_______|
| | | | | | |
| __| | | Deg. | Mins. | Mins. |
| | 20 | 80 | 137 | 3 | 4 |
| | 30 | 70 | 160 | 3 | 4 |
| | 40 | 60 | 180 | 7 | 18 |
| | | | | | No |
| | | | | | fumes |
| | | | | | after |
| From 'A' sample. | 50 | 50 | 187.5 | 55 | 100 |
| | 60 | 40 | 187 | 45 | 100 |
| | 70 | 30 | 185 | 45 | 100 |
| | 80 | 20 | | 50 | 100 |
| __| 92 | 8 | 185 | 50 | 100 |
| | Structure- | | | | |
| | less powder. | | | | |
| " 'B' sample __| 50 | 50 | 183 | 35 | 100 |
| " 'C' sample | Ordinary service | 185 | 10 | 41 |
| | guncotton | | | |
|___________________|______________|_________|_____________|_______|_______|
a certain solvent action, and on adding an equal bulk of water, the
dissolved nitrate for the most part is precipitated, at the same time
that the undissolved but disintegrated and swollen product undergoes
further changes in the direction of increase of hardness and density.
The product being now collected on a filter, freed from acetone by
washing with water and dried, is a hard and dense powder the fineness of
which varies according to the attendant conditions of treatment. With
the main product in certain cases there is found associated a small
proportion of nitrate retaining a fibrous character, which may be
separated by means of a fine sieve. On examining such a residue, we
found it to contain only 5.6 p.ct. N, and as it was insoluble in strong
acetone, it may be regarded as a low nitrate or a mixture of such with
unaltered cellulose. Confirming this we found that the product passing
through the sieve showed an increase of nitrogen to 13.43 p.ct. from the
13.31 p.ct. in the original. Tested by the heat test (50 minutes) and
stability test (no fumes after 100 minutes), we found the products to
have the characteristics previously noticed.
It is clear, therefore, that this specifically regulated action of
acetone produces the effects (a) of disintegration, and (b)
stabilisation. It remains to determine whether the latter effect was
due, as might be supposed, to the actual elimination of a compound or
group of compounds present in the original nitrate, and to be regarded
as the effective cause of instability. It is to be noted first that as a
result of the treatment with the diluted acetone and further dilution
after the specific action is completed, collecting the disintegrated
product on a filter and washing with water, the loss of weight sustained
amounts to 3 to 4 p.ct. This loss is due, therefore, to products
remaining dissolved in the filtrate--that is to say, in the much diluted
acetone. These filtrates are in fact opalescent from the presence of a
portion of nitrate in a colloidal (hydrated) form. On distilling off the
acetone, a precipitation is determined. The precipitates are nitrates of
variable composition, analysis showing from 9 to 12 p.ct. of nitric
nitrogen. The filtrate from these precipitates containing only
fractional residues of acetone still shows opalescence. On
long-continued boiling a further precipitation is determined, the
filtrates from which are clear. It was in this final clear filtrate that
the product assumed to cause the instability of the original nitrate
would be present. The quantity, however, is relatively so small that we
have only been able to obtain and examine it as residue from evaporation
to dryness. An exhaustive qualitative examination established a number
of negative characteristics, with the conclusion that the products were
not direct derivatives of carbohydrates nor aromatic compounds. On the
other hand the following positive points resulted. Although the original
diluted acetone extract was neutral to test papers, yet the residue was
acid in character. It contained combined nitric groups, fused below 200 deg.
giving off acid vapours, and afterwards burning with a smoky flame. On
adding lead acetate to the original clear solution, a well-marked
precipitation was determined. The lead compounds thus isolated are
characteristic. They have been obtained in various ways and analysed.
The composition varies with the character of the solution in which the
lead compound is formed. Thus in the opalescent or milky solutions in
which a proportion of cellulose nitrate is held in solution or
semi-solution by the acetone still present, the lead acetate causes a
dense coagulation. The precipitates dried and analysed showed 16-20
p.ct. PbO and 11-9 p.ct. N. It is clear that the cellulose nitrates are
associated in these precipitates with the lead salts of the acid
compounds in question. When the latter are obtained from clear
solutions, i.e. in absence of cellulose nitrates, they contain 60-63
p.ct. PbO and 3.5 p.ct. N (obtained as NO).
In further confirmation of the conclusion from these results, viz. that
the nitrocelluloses with no tendency to combine with PbO are associated
with acid products or by-products of the ester reaction combining with
the oxide, the lead reagent was allowed to react in the presence of 90
p.ct. acetone. Water was added, the disintegrated mass collected, washed
with dilute acetic acid, and finally with water. Various estimations of
the PbO fixed in this way have given numbers varying from 2 to 2.5 p.ct.
Such products are perfectly stable. This particular effect of
stabilisation appears, therefore, to depend upon the combination of
certain acid products present in ordinary nitrocelluloses with metallic
oxides. In order to further verify this conclusion, standard specimens
of cellulose nitrates have been treated with a large number of metallic
salts under varying conditions of action. It has been finally
established (1) that the effects in question are more particularly
determined by treatment with salts of lead and zinc, and (2) that the
simplest method of treatment is that of boiling the cellulose nitrates
with dilute aqueous solutions of salts of these metals, preferably the
acetates. The following results may be cited, obtained by boiling a
purified 'service' guncotton (sample C) with a 1 p.ct. solution of lead
acetate and of zinc acetate respectively. After boiling 60 minutes the
nitrates were washed free from the soluble metallic salts, dried and
tested.
__________________________________________________
| | | |
| | Heat Test | Heat Test |
| | at 80 deg. | at 134 deg. |
|__________________________|___________|___________|
| | | |
| Original sample C | 10 | 41 |
|Treated with lead acetate | 67 | 45 |
| " zinc " | 91 | 45 |
|__________________________|___________|___________|
In conclusion we may briefly resume the main points arrived at in these
investigations.
_Causes of instability of cellulose nitrates._--The results of our
experiments so far as to the causes of instability in cellulose nitrates
may be summed up as follows:--
(1) Traces of free nitrating acids, which can only occur in the finished
products through careless manufacture, will undoubtedly cause
instability, indicated strongly by the ordinary heat test at 80 deg., and to
a less extent by the heat test at 134 deg..
(2) Other compounds exist in more intimate association with the
cellulose nitrates causing instability which cannot be removed by
exhaustive washing with either hot or cold water, by digestion in cold
dilute alkaline solutions such as sodium carbonate, or by extracting
with ether, alcohol, benzene, &c.; these compounds, however, are soluble
in the solvents of highly nitrated cellulose such as acetone, acetic
ether, pyridine, &c., even when these liquids are so diluted with water
or other non-solvent liquids to such an extent that they have little or
no solvent action upon the cellulose nitrate itself. These solutions
containing the bodies causing instability are neutral to test paper, but
become acid upon evaporation by heating. (This probably explains the
presence of free acid when guncotton is purified by long-continued
boiling in water without any neutralising agent being present.)
(3) The bodies causing instability are products or by-products of the
original ester reaction, acid bodies containing nitroxy-groups, but
otherwise of ill-defined characteristics. They combine with the oxides
of zinc or lead, giving insoluble compounds. They are precipitated from
their solutions in diluted acetone upon the addition of soluble salts of
these metals.
(4) Cellulose nitrates are rendered stable either by eliminating these
compounds, or by combining them with the oxides of lead or zinc whilst
still in association with cellulose nitrates.
(5) Even the most perfectly purified nitrocellulose will slowly
decompose with formation of unstable acid products by boiling for a long
time in water. This effect is much more apparent at higher temperatures.
_Dense structureless or non-fibrous cellulose nitrates_ can be
industrially prepared (1) by nitrating the amorphous forms of cellulose
obtained from its solution as sulphocarbonate (viscose). The cellulose
in this condition reacts with the closest similarity to the original
fibrous cellulose; the products are similar in composition and
properties, including that of instability.
(2) By treating the fibrous cellulose nitrates with liquid solvents of
the high nitrate diluted with non-solvent liquids, and more especially
water. The optimum effect is a specific disintegration or breaking down
of their fibrous structure quite distinct from the gelatinisation which
precedes solution in the undiluted solvent, and occurring within narrow
limits of variation in the proportion of the diluting and non-solvent
liquid--for industrial work the most convenient solution to employ is
acetone diluted with about 10 p.ct. of water by volume.
The industrial applications of these results are the basis of English
patents 5286 (1898), 18,868 (1898), 18,233 (1898), Luck and Cross (this
Journal, 1899, 400, 787).
The structureless guncotton prepared as above described is of quite
exceptional character, and entirely distinct from the ordinary fibrous
nitrate or the nitrate prepared by precipitation from actual solution in
an undiluted solvent.[3] By the process described, the nitrate is
obtained at a low cost in the form of a very fine, dense, structureless,
white powder of great purity and stability, entirely free from all
mechanical impurities. The elimination of these mechanical impurities,
and also to a very great extent of coloured compounds contained in the
fibrous nitrate, makes the product also useful in the manufacture of
celluloids, artificial silk, &c., whilst its very dense form gives it a
great advantage over ordinary fibrous guncotton for use in shells and
torpedoes, and for the manufacture of gelatinised gunpowders, &c. It can
be compressed with ease into hard masses; and experiments are in
progress with a view of producing from it, in admixture with 'retaining'
ingredients, a military explosive manufactured by means of ordinary
black gunpowder machinery and processes.
_Manufacture of sporting powder._--The fact that the fibrous structure
of ordinary guncotton or other cellulose nitrate can be completely or
partially destroyed by treatment with diluted acetone and without
attendant solution, constitutes a process of value for the manufacture
of sporting powder having a base of cellulose nitrate of any degree of
nitration. The following is a description of the hardening process.
'Soft grains' are manufactured from ordinary guncotton or other
cellulose nitrate either wholly or in combination with other
ingredients, the process employed being the usual one of revolving in a
drum in the damp state and sifting out the grains of suitable size after
drying. These grains are then treated with diluted acetone, the degree
of dilution being fixed according to the hardness and bulk of the
finished grain it is desired to produce (J. Soc. Chem. Ind., 1899, 787).
Owing to the wide limits of dilution and corresponding effect, the
process allows of the production of either a 'bulk' or a 'condensed'
powder.
We prefer to use about five litres of the liquid to each one kilo. of
grain operated upon, as this quantity allows of the grains being freely
suspended in the liquid upon stirring. The grains are run into the
liquid, which is then preferably heated to the boiling-point for a few
minutes whilst the whole is gently stirred. Under this treatment the
grains assume a more or less rounded gelatinous condition according to
the strength of the liquid. There is, however, no solution of the
guncotton and practically no tendency of the grains to cohere. Each
grain, however, is acted upon _throughout_ and perfectly _equally_.
After a few minutes' treatment, water is gradually added, when the
grains rapidly harden. They are then freed from acetone and certain
impurities by washing with water, heating, and drying. The process is of
course carried out in a vessel provided with any means for gentle
stirring and heating, and with an outlet for carrying off the
volatilised solvent which is entirely recovered by condensation, the
grains parting with the acetone with ease.
_Stabilising cellulose nitrates._--The process is of especial value in
rendering stable and inert the traces of unstable compounds which always
remain in cellulose nitrate after the ordinary boiling and washing
process. It is of greatest value in the manufacture of collodion cotton
used for the preparation of gelatinous blasting explosives and all
explosives composed of nitroglycerin and cellulose nitrates. Such
mixtures seem peculiarly liable to decomposition if the cellulose
nitrate is not of exceptional stability (J. Soc. Chem. Ind., 1899,
787).
EMPLOI DE LA CELLULOSE POUR LA FABRICATION DE FILS BRILLANTS IMITANT LA
SOIE.
E. BRONNERT (1) (Rev. Mat. Col., 1900, September, 267).
V. ~USE OF CELLULOSE IN THE MANUFACTURE OF IMITATIONS OF SILK
(LUSTRA-CELLULOSE).~
(p. 45) _Introduction._--The problem of spinning a continuous thread of
cellulose has received in later years several solutions. Mechanically
all resolve themselves into the preparation of a structureless filtered
solution of cellulose or a cellulose derivative, and forcing through
capillary orifices into some medium which either absorbs or decomposes
the solvent. The author notes here that the fineness and to a great
extent the softness of the product depends upon the dimensions of the
capillary orifice and concentration of the solution. The technical idea
involved in the spinning of artificial fibres is an old one. Reaumur (2)
forecast its possibility, Audemars of Lausanne took a patent as early as
1855 (3) for transforming nitrocellulose into fine filaments which he
called 'artificial silk.' The idea took practical shape only when it
came to be used in connection with filaments for incandescent lamps. In
this connection we may mention the names of the patentees:--Swinburne
(4), Crookes, Weston (5), Swan (6), and Wynne and Powell (7). These
inventors prepared the way for Chardonnet's work, which has been
followed since 1888 with continually increasing success.
At this date the lustra-celluloses known may be divided into four
classes.
1. 'Artificial silks' obtained from the nitrocelluloses.
2. 'Lustra-cellulose' made from the solution of cellulose in
cuprammonium.
3. 'Lustra-cellulose' prepared from the solution of cellulose in
chloride of zinc.
4. 'Viscose silks,' by the decomposition of sulphocarbonate of cellulose
(Cross and Bevan).
GROUP 1. The early history of the Chardonnet process is discussed and
some incidental causes of the earlier failures are dealt with. The
process having been described in detail in so many publications the
reader is referred to these for details. [See Bibliography, (1) and (2),
(3) and (4).] The denitrating treatment was introduced in the period
1888-90 and of course altogether changed the prospects of the industry;
not only does it remove the high inflammability, but adds considerably
to softness, lustre, and general textile quality. In Table I will be
found some important constants for the nitrocellulose fibre; also the
fibre after denitration and the comparative constants for natural silk.
TABLE 1.
_______________________________________________________________________
| | | |
| | Tenacity | Elasticity |
| | (grammes) | (% elongation) |
|__________________________________________|___________|________________|
| | | |
| Nitrocellulose according to Chardonnet | | |
| German Patent No. 81,599 | 150 | 23 |
| The same after denitration | 110 | 8 |
| Denitrated fibre moistened with water | 25 | -- |
| Nitrocellulose: Bronnert's German Patent | | |
| No. 93,009 | 125 | 28 |
| The same after denitration (dry) | 115 | 13 |
| The same after denitration (wetted) | 32 | -- |
| Natural silk | 300 | 18 |
|__________________________________________|___________|________________|
1. Tenacity is the weight in grammes required to break the
thread.
2. Elasticity is the elongation per cent. at breaking.
The numbers are taken for thread of 100 deniers (450 metres of
0.05 grammes = 1 denier). It must be noted that according to
the concentration of the solution and variations in the process
of denitration the constants for the yarn are subject to very
considerable variation.
In regard to the manufacture a number of very serious difficulties have
been surmounted. First, instead of drying the nitrated cellulose, which
often led to fires, &c., it was found better to take it moist from the
centrifugal machine, in which condition it is dissolved (5). It was
next found that with the concentrated collodion the thread could be spun
direct into the air, and the use of water as a precipitant was thus
avoided.
With regard to denitration which is both a delicate and disagreeable
operation: none of the agents recommended to substitute the sulphydrates
have proved available. Of these the author mentions ferrous chloride
(6), ferrous chloride in alcohol (7), formaldehyde (8),
sulphocarbonates. The different sulphydrates (9) have very different
effects. The calcium compound tends to harden and weaken the thread. The
ammonia compound requires great care and is costly. The magnesium
compound works rapidly and gives the strongest thread. Investigations
have established the following point. In practice it is not necessary to
combine the saponification of cellulose ester with complete reduction of
the nitric acid split off. The latter requires eight molecules of
hydrogen sulphide per one molecule tetranitrocellulose, but with
precautions four molecules suffice. It is well known that the
denitration is nearly complete, traces only of nitric groups surviving.
Their reactions with diphenylamine allow a certain identification of
artificial silks of this class. Various other inventors, e.g. Du Vivier
(10), Cadoret (11), Lehner (12), have attempted the addition of other
substances to modify the thread. These have all failed. Lehner, who
persisted in his investigations, and with success, only attained this
success, however, by leaving out all such extraneous matters. Lehner
works with 10 p.ct. solutions; Chardonnet has continually aimed at
higher concentration up to 20 p.ct. Lehner has been able very much to
reduce his pressures of ejection in consequence; Chardonnet has had to
increase up to pressures of 60 k. per cm. and higher. The latter
involves very costly distributing apparatus. Lehner made next
considerable advance by the discovery of the fact that the addition of
sulphuric acid to the collodion caused increase of fluidity (13), which
Lehner attributes to molecular change. Chardonnet found similar results
from the addition of aldehyde and other reagents (14), but not such as
to be employed for the more concentrated collodions. The author next
refers to his discoveries (15) that alcoholic solutions of a number of
substances, organic and inorganic, freely dissolve the lower cellulose
nitrates. The most satisfactory of these substances is chloride of
calcium (16). It is noted that acetate of ammonia causes rapid changes
in the solution, which appear to be due to a species of hydrolysis. The
result is sufficiently remarkable to call for further investigation. The
chloride of calcium, it is thought possible, produces a direct
combination of the alcohol with a reactive group of the nitrocellulose.
The fluidity of this solution using one mol. CaCl_{2} per 1 mol.
tetranitrate (17) reaches a maximum in half an hour's heating at
60 deg.-70 deg.C. The fluidity is increased by starting from a cotton which has
been previously mercerised. After nitration there is no objection to a
chlorine bleach. Chardonnet has found on the other hand that in
bleaching before nitration there is a loss of spinning quality in the
collodion. The author considers that the new collodion can be used
entirely in place of the ordinary ether-alcohol collodion. With regard
to the properties of the denitrated products they fix all basic colours
without mordant and may be regarded as oxycellulose therefore. The
density of the thread is from 1.5 to 1.55. The thread of 100 deniers
shows a mean breaking strain of 120 grammes with an elasticity of 8-12
p.ct. The cardinal defect of these fibres is their property of
combination with water. Many attempts have been made to confer
water-resistance (18), but without success. Strehlenert has proposed the
addition of formaldehyde (19), but this is without result (20). In
reference to these effects of hydration, the author has made
observations on cotton thread, of which the following table represents
the numerical results:
Breaking Strain
Mean of 20 experiments
Skein of bleached cotton without treatment 825
Skein of bleached cotton without treatment, but wetted 942
Ditto after conversion into hexanitrate, dry 884
The above, wetted 828
The cotton denitrated from above, dry 529
The cotton denitrated as above and wetted 206
The author considers that other patents which have been taken for
spinning nitrocellulose are of little practical account (21) and (22).
The same conclusion also applies to the process of _Langhans_, who
proposes to spin solutions of cellulose in sulphuric acid (23) (24) and
mixtures of sulphuric acid and phosphoric acid.
GROUP 2. _Lustra-cellulose._--Thread prepared by spinning solutions of
cellulose in cuprammonium.
This product is made by the Vereinigte Glanzstoff-Fabriken, Aachen,
according to a series of patents under the names of H. Pauly, M. Fremery
and Urban, Consortium mulhousien pour la fabrication de fils brillants,
E. Bronnert, and E. Bronnert and Fremery and Urban (1). The first patent
in this direction was taken by Despeissis in 1890 (2). It appears this
inventor died shortly after taking the patent (3) The matter was later
developed by Pauly (4) especially in overcoming the difficulty of
preparing a solution of sufficient concentration. (It is to be noted
that Pauly's patents rest upon a very slender foundation, being
anticipated in every essential detail by the previous patent of
Despeissis.) For this very great care is required, especially, first,
the condition of low temperature, and, secondly, a regulated proportion
of copper and ammonia to cellulose. The solution takes place more
rapidly if the cellulose has been previously oxidised. Such cellulose
gives an 8 p.ct. solution, and the thread obtained has the character of
an oxycellulose, specially seen in its dyeing properties. The best
results are obtained, it appears, by the preliminary mercerising
treatment and placing the alkali cellulose in contact with copper and
ammonia. (All reagents employed in molecular proportions.) The author
notes that the so-called hydrocellulose (Girard) (5) is almost insoluble
in cuprammonium, as is starch. It is rendered soluble by alkali
treatment.
GROUP 3. _Lustra-cellulose_ prepared by spinning a solution of cellulose
in concentrated chloride of zinc.
This solution has been known for a long time and used for making
filaments for incandescent lamps. The cellulose threads, however, have
very little tenacity. This is no doubt due to the conditions necessary
for forming the solution, the prolonged digestion causing powerful
hydrolysis (1). Neither the process of Wynne and Powell (2) nor that of
Dreaper and Tompkins (3), who have endeavoured to bring the matter to a
practical issue, are calculated to produce a thread taking a place as a
textile. The author has described in his American patent (4) a method of
effecting the solution in the cold, viz. again by first mercerising the
cellulose and washing away the caustic soda. This product dissolves in
the cold and the solution remains unaltered if kept at low temperature.
Experiments are being continued with these modifications of the process,
and the author anticipates successful results. The modifications having
the effect of maintaining the high molecular weight of the cellulose, it
would appear that these investigations confirm the theory of Cross and
Bevan that the tenacity of a film or thread of structureless regenerated
cellulose is directly proportional to the molecular weight of the
cellulose, i.e. to its degree of molecular aggregation (5).
GROUP 4. 'Viscose' silks obtained by spinning solutions of xanthate of
cellulose.
In 1892, Cross and Bevan patented the preparation of a new and curious
compound of cellulose, the thiocarbonate (1) (2) (3). Great hopes were
based upon this product at the time of its discovery. It was expected
to yield a considerable industrial and financial profit and also to
contribute to the scientific study of cellulose. The later patents of C.
H. Stearn (4) describe the application of viscose to the spinning of
artificial silk. The viscose is projected into solutions of chloride of
ammonium and washed in a succession of saline solutions to remove the
residual sulphur impurities. The author remarks that though it has a
certain interest to have succeeded in making a thread from this compound
and thus adding another to the processes existing for this purpose, he
is not of opinion that it shows any advance on the lustra-cellulose (2)
and (3). He also considers that the bisulphide of carbon, which must be
regarded as a noxious compound, is a serious bar to the industrial use
of the process, and for economic work he considers that the regeneration
of ammonia from the precipitating liquors is necessary and would be as
objectionable as the denitration baths in the collodion process. The
final product not being on the market he does not pronounce a finally
unfavourable opinion.
The author and the Vereinigte Glanzstoff-Fabriken after long
investigation have decided to make nothing but the lustra-cellulose (2)
and (3). A new factory at Niedermorschweiler, near Mulhouse, is
projected for this last production.
BIBLIOGRAPHY
_Introduction_
(1) Bull. de la Soc. industr. de Mulhouse, 1900.
(2) Reaumur, Memoire pour servir a l'histoire des insectes, 1874, 1, p.
154.
(3) English Pat. No. 283, Feb. 6, 1855.
(4) Swinburne, Electrician, 18, 28, 1887, p. 256.
(5) Weston (Swinburne), Electrician, 18, 1887, p. 287. Eng. Pat. No.
22866, Sept. 12, 1882.
(6) German Pat. No. 3029. English Pat. No. 161780, April 28, 1884
(Swan).
(7) Wynne-Powell, English Pat. No. 16805, Dec. 22, 1884.
_Group I_
(1) German Pat No. 38368, Dec. 20, 1885. German Pat. No. 46125, March 4,
1888. German Pat. No. 56331, Feb. 6, 1890. German Pat. No. 81599, Oct.
11, 1893. German Pat. No. 56655, April 23, 1890. French Pat. No. 231230,
June 30, 1893.
(2) Industrie textile, 1899, 1892. Wyss-Noef, Zeitschrift fuer angewandte
Chemie, 1899, 30, 33. La Nature, Jan. 1, 1898, No. 1283. Revue generale
des sciences, June 30, 1898.
(3) German Pat. No. 46125, March 4, 1888. German Pat. No. 56655, April
23, 1890.
(4) Swan, English Pat. 161780, June 28, 1884. See also Bechamp, Dict. de
Chimie de Wurtz.
(5) German Pat. No. 81599, Oct 11, 1893.
(6) Bechamp, art. Cellulose, Dict. de Chimie de Wurtz, p. 781.
(7) Chardonnet, addit. March 3, 1897, to the French Pat. 231230, May 30,
1893.
(8) Knofler, French Pat. 247855, June 1, 1895. German Pat. 88556, March
28, 1894.
(9) Bechamp, art. Cellulose, Dict. de Chimie de Wurtz. Blondeau, Ann.
Chim. et Phys. (3), 1863, 68, p. 462.
(10) Revue industrielle, 1890, p. 194. German Pat. 52977, March 7, 1889.
(11) French Pat. 256854, June 2, 1896.
(12) German Pat. 55949, Nov. 9, 1889. German Pat. 58508, Sept. 16, 1890.
German Pat. 82555, Nov. 15, 1894.
(13) German Pat. 58508, Sept. 16, 1900.
(14) French Pat. 231230, June 30, 1893.
(15) German Pat. 93009, Nov. 19, 1895. French Pat. 254703, March 12,
1896. English Pat. 6858, March 28, 1896.
(16) American Pat. 573132, Dec. 15, 1896.
(17) This proportion is the most advantageous, and furnishes the best
liquid collodions that can be spun.
(18) French Pat. 259422, Sept. 3, 1896.
(19) English Pat. 22540, 1896.
(20) Application for German Pat. not granted, 4933 IV. 296, Mar. 16,
1897.
(21) German Pat. 96208, Feb. 10, 1897. Addit. Pat. 101844 and 102573,
Dec. 10, 1897.
(22) Oberle et Newbold, French Pat. 25828, July 22, 1896. Granquist,
Engl. applic. 2379, Nov. 28, 1899.
(23) German Pat. 72572, June 17, 1891.
(24) Voy. Stern, Ber., 28, ch. 462.
_Group II_
(1) German Pat. 98642, Dec. 1, 1897 (Pauly). French Pat. 286692, March
10, 1899, and addition of October 14, 1899 (Fremery and Urban). French
Pat. 286726, March 11, 1899, and addition of December 4, 1899. German
Pat. 111313, March 16, 1899 (Fremery and Urban). English Pat. 18884,
Sept. 19, 1899 (Bronnert). English Pat. 13331, June 27, 1899 (Consort.
mulhousien).
(2) French Pat. 203741, Feb. 12, 1890.
(3) The actual lapse of this patent is due to the death of Despeissis
shortly after it was taken.
(4) Without questioning the good faith of Pauly, it is nevertheless a
fact that the original patent remains as a document, and therefore that
the value of the Pauly patents is very questionable.
(5) Girard, Ann. Chim. et Phys, 1881 (5), 24, p. 337-384.
_Group III_
(1) Cross and Bevan, Cellulose, 1895, p. 8.
(2) English Pat. 16805, Dec. 22, 1884.
(3) English Pat. 17901, July 30, 1897.
(4) Bronnert, American Pat. 646799, April 3, 1900.
(5) Cross and Bevan, Cellulose, 1895, p. 12.
_Group IV_
(1) English Pat. 8700, 1892. German Pat. 70999, Jan. 13, 1893.
(2) English Pat. 4713, 1896. German Pat. 92590, Nov. 21, 1896.
(3) Comptes rendus (loc. cit.). Berichte, c. 9, 65a.
(4) English Pat. 1020, 1898. German Pat. 108511, Oct. 18, 1898.
~Artificial Silk--Lustra-cellulose.~
C. F. CROSS and E. J. BEVAN (J. Soc. Chem. Ind., 1896, 317).
The object of this paper is mainly to correct current statements as to
the artificial or 'cellulose silks' being explosive or highly
inflammable (ibid., 1895, 720). A specimen of the 'Lehner' silk was
found to retain only 0.19 p.ct. total nitrogen, showing that the
denitration is sufficiently complete to dispose of any suggestion of
high inflammability.
The product yielded traces only of furfural; on boiling with a 1 p.ct.
solution of sodium hydrate, the loss of weight was 9.14 p.ct.; but the
solution had no reducing action on Fehling's solution. The product in
denitration had therefore reverted completely to a cellulose (hydrate),
no oxy-derivative being present.
* * * * *
The authors enter a protest against the term 'artificial silk' as
applied to these products, and suggest 'lustra-cellulose.'
DIE KUeNSTLICHE SEIDE-IHRE HERSTELLUNG, EIGENSCHAFTEN UND VERWENDUNG.
CARL SUeVERN, Berlin, 1900, J. Springer.
~ARTIFICIAL SILK--ITS PRODUCTION, PROPERTIES, AND APPLICATIONS.~
This work of some 130 pages is an important monograph on the subject of
the preparation of artificial cellulose threads--so far as the technical
elements of the problems involved are discussed and disclosed in the
patent literature. The first section, in fact, consists almost
exclusively of the several patent specifications in chronological order
and ranged under the sub-sections: (a) The Spinning of Nitrocellulose
(collodion); (b) The Spinning of other Solutions of Cellulose; (c)
The Spinning of Solutions of the Nitrogenous Colloids.
In the second section the author deals with the physical and chemical
proportions of the artificial threads.
_Chardonnet 'silk'_ is stated to have a mean diameter of 35 mu, but with
considerable variations from the mean in the individual fibres; equally
wide variations in form are observed in cross-section. The general form
is elliptical, but the surface is marked by deep striae, and the
cross-section is therefore of irregular outline. This is due to
irregular conditions of evaporation of the solvents, the thread being
'spun' into the air from cylindrical orifices of regulated dimensions.
Chardonnet states that when the collodion is spun into alcohol the
resultant thread is a perfect cylinder (Compt. rend. 1889, 108, 962).
The strength of the fibre is variously stated at from 50-80 p.ct. that
of 'boiled off' China tram; the true elasticity is 4-5 p.ct., the
elongation under the breaking strain 15-17 p.ct. The sp.gr. is 1.49,
i.e. 3-5 p.ct. in excess of boiled off silk.
_Lehner 'silk'_ exhibits the closest similarity to the Chardonnet
product. In cross-section it is seen to be more regular in outline, and
a round, pseudo-tubular form prevails, due to the conditions of
shrinkage and collapse of the fibre in parting with the solvents, and in
then dehydrating. The constants for 'breaking strain,' both in the
original and moistened condition, for elasticity, &c., are closely
approximate to those for the Chardonnet product.
_Pauly 'silk'._--The form of the ultimate fibres is much more regular
and the contour of the cross-section is smooth. The product shows more
resistance to moisture and to alkaline solutions.
_Viscose 'silk'_ is referred to in terms of a communication appearing in
'Papier-Zeitung,' 1898, 2416.
In the above section the following publications are referred
to: Chardonnet, 'Compt. rend.,' 1887, 105, 900; and 1889, 108,
962; Silbermann, 'Die Seide,' 1897, v. 2, 143; Herzog,
'Farber-Zeitung,' 1894/5, 49-50; Thiele, ibid. 1897, 133; O.
Schlesinger, 'Papier-Zeitung,' 1895, 1578-81, 1610-12.
_Action of Reagents upon Natural and Artificial Silks._
1. _Potassium hydrate_ in solution of maximum concentration dissolves
the silks proper, (a) China silk on slight warming, (b) Tussah silk
on boiling. The cellulose 'silks' show swelling with discolouration, but
the fibrous character is not destroyed even on boiling.
2. _Potassium hydrate_ 40 p.ct. China silk dissolves completely at
65 deg.-85 deg.; Tussah silk swells considerably at 75 deg. and dissolves at
100 deg.-120 deg.. The cellulose 'silks' are attacked with discolouration; at
140 deg. (boiling-point of the solution) there is progressive solvent
action, but the action is incomplete. The Pauly product is most
resistant.
3. _Zinc chloride_, 40 p.ct. solution. Both the natural silks and
lustra-celluloses are attacked at 100 deg., and on raising the temperature
the further actions are as follows: China silk is completely dissolved
at 110-120 deg.; Tussah silk at 130-135 deg.; the collodion products at
140-145 deg.; the Pauly product was again most resistant, dissolving at
180 deg..
4. _Alkaline cupric oxide_ (glycerin) solution was prepared by
dissolving 10 grs. of the sulphate in 100 c.c. water, adding 5 grs.
glycerin and 10 c.c. of 40 p.ct. KOH. In this solution the China silk
dissolved at the ordinary temperature; Tussah silk and the
lustra-celluloses were not appreciably affected.
5. _Cuprammonium solution_ was prepared by dissolving the precipitated
cupric hydrate in 24 p.ct. ammonia. In this reagent also the China silk
dissolved, and the Tussah silk as well as the lustra-celluloses
underwent no appreciable change.
6. _An ammoniacal solution of nickel oxide_ was prepared by dissolving
the precipitated hydrated oxide in concentrated ammonia. The China silk
was dissolved by this reagent; Tussah silk and the lustra-celluloses
entirely resisted its action.
7. _Fehling's solution_ is a solvent of the natural silks, but is
without action on the lustra-celluloses.
8. _Chromic acid_--20 p.ct. CrO_{3}--solution dissolves both the natural
silks and the lustra-celluloses at the boiling temperature of the
solution.
9. _Millon's reagent_, at the boiling solution, colours the natural
silks violet: the lustra-celluloses give no reaction.
10. _Concentrated nitric acid_ attacks the natural silks powerfully in
the cold; the lustra-celluloses dissolve on heating.
11. _Iodine solution_ (I in KI) colours the China silk a deep brown,
Tussah a pale brown; the celluloses from collodion are coloured at first
brown, then blue. The Pauly product, on the other hand, does not react.
12. _Diphenylamine sulphate._--A solution of the base in concentrated
sulphuric acid colours the natural silks a brown; the collodion 'silks'
give a strong blue reaction due to the presence of residual
nitro-groups. The Pauly product is not affected.
13. _Brucin sulphate_ in presence of concentrated sulphuric acid colours
the natural silks only slightly (brown); the collodion 'silks' give a
strong red colouration. The Pauly product again is without reaction.
14. _Water._--The natural silks do not soften in the mouth as do the
lustra-celluloses.
15. _Water of condition_ was determined by drying at 100 deg.; the following
percentages resulted (a). The percentages of water (b) taken up from
the atmosphere after forty-three hours' exposure were:
(a) (b)
China (raw) silk 7.97 2.24
Tussah silk 8.26 5.00
Lustra-celluloses:
Chardonnet (Besancon) 10.37 5.64
" Spreitenbach 11.17 5.77
Lehner 10.71 5.97
Pauly 10.04 6.94
16. _Behaviour on heating at 200 deg.._--After two hours' heating at this
temperature the following changes were noted:
China silk Much discoloured (brown).
Tussah silk Scarcely affected.
Lustra-celluloses:
Chardonnet Converted into a blue-black charcoal, retaining the
Lehner form ofthe fibres.
Pauly A bright yellow-brown colouration, without carbonisation.
17. The _losses of weight_ accompanying these changes and calculated per
100 parts of fibre dried at 100 deg. were:
China silk 3.18
Tussah silk 2.95
Lustra-celluloses:
Chardonnet 33.70
Lehner 26.56
Pauly 1.61
18. _Inorganic constituents._--Determinations of the total ash gave for
the first five of the above, numbers varying from 1.0 to 1.7 p.ct. The
only noteworthy point in the comparison was the exceptionally small ash
of the Pauly product, viz. 0.096 p.ct.
19. _Total nitrogen._--The natural silks contain the 16-17 p.ct. N
characteristic of the proteids. The lustra-celluloses contain 0.05-0.15
p.ct. N which in those spun from collodion is present in the form of
nitric groups.
The points of chemical differentiation which are established by the
above scheme of comparative investigation are summed up in tabular form.
_Methods of dyeing._--The lustra-celluloses are briefly discussed. The
specific relationship of these forms of cellulose to the colouring
matters are in the main those of cotton, but they manifest in the
dye-bath the somewhat intensified attraction which characterises
mercerised cotton, or more generally the cellulose hydrates.
_Industrial applications_ of the lustra-celluloses are briefly noticed
in the concluding section of the book.
FOOTNOTES:
[3] With these products it is easy to observe that they have a definite
fusion point 5 deg.-10 deg. below the temperature of explosion.